The major thrust of this study is to elucidae the molecular genetics of neoplastic transformation of normal tissues and the action of a biological modifier in cellular defense mechanism. Two experimental systems were used: 1) Two rat leukemia helper viruses - a) KSV(RHHV) originally isolated in this laboratory and b) WR-RaLV, a wild rat tumor virus, and 2) Interleukin 2, a rat spleen cell product. Multidisciplinary approaches involving nucleic acid and protein chemitry, recombinant DNA, and tissue culture were employed. We have earlier completed extensive morphological, biological, biochemical and immunological characterizations of these retroviruses. Our current interests focus on the molecular mechanisms involved in the evolution of a transforming DNA sequence through the recombination between a RaLV DNA sequence and rat endogeneous DNA sequence c-src. Our total research efforts are concentrated on: 1) Molecular cloning and recombinant DNA analysis, 2) Restriction endonuclease map, 3) Functional organization, 4) Heterduplex analysis of conservation and divergency in nucleotide sequences, 5) Microinjection of RaLV total and subgenomic DNA sequences for DNA transduction analysis and 6) Immediate and long term effects of interleukin 2 on T-lymphocytes and natural killer cells in cellular defense mechanism.